Enantioselective synthesis of (L)-Fmoc-α-Me-Lys(Boc)-OH via diastereoselective alkylation of oxazinone as a chiral auxiliary
✍ Scribed by Satendra S. Chauhan
- Publisher
- Elsevier Science
- Year
- 2009
- Tongue
- French
- Weight
- 238 KB
- Volume
- 50
- Category
- Article
- ISSN
- 0040-4039
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✦ Synopsis
Benzyl (2R,3S)-(À)-6-oxo-2,3-diphenyl-4-morpholinecarboxylate (4) was successively alkylated with methyl iodide and 1,4-diiodobutane using a base. In each alkylation step anti-alkylated product formed exclusively. The iodo group was displaced with azide, which served as a precursor for the side-chain amino function. Catalytic hydrogenation with concomitant cleavage of the chiral auxiliary afforded (L)a-Me-Lys-OH (9) in a total of four steps in good yield. (L)-Fmoc-a-Me-Lys(Boc)-OH ( 16) was obtained from 9 via regioselective benzyloxycarbonylation. Alternately, (L)-Fmoc-a-Me-Lys(Boc)-OH ( 16) was obtained via Staudinger reduction of azide (8) in a total of six steps in good yield.